1. Field of the Invention
The present disclosure relates generally to ultrasound image processing and, more particularly, to estimating gestation age of a fetus from an ultrasound image.
2. Description of Related Art
Obstetric ultrasound imaging is used for a variety of purposes. Some of the information that can be monitored includes that of a fetal heart beat, malformations in the fetus, diagnosis and confirmation of early pregnancy, and the like. Further, measurements such as Crown-rump length, Femur length, abdominal circumference, Head Circumference (HC) and Bi-Parietal Diameter (BPD) can also be taken.
The length of the BPD can be used in assessing the gestational age of a fetus, especially during late first and second trimesters. The BPD length can be measured manually, using a caliper to read the distance on a fetal head image. This technique, however, can prove to be time consuming, cumbersome, and is prone to intra-observer and inter-observer variability.
Semi-automated and automated techniques for estimating the BPD length are also currently available. These techniques assume the fetal head to be an ellipse and then compute the BPD length as the length of the minor axis of the ellipse. A variety of approaches are used in the segmentation of the fetal head image as an ellipse. One such approach makes use of a semi-automated method in which the user marks a contour inside the fetal head. The contour is then used as an initialization to an active contour model which suitably inflates or deflates on the basis of an energy function.
According to another approach the fetal head is assumed to be elliptical and its parameters are estimated by means of iterative randomized Hough transform. Yet another approach utilizes pattern recognition techniques. In this approach, a set of training images, typically containing hundreds of images, having a labeled fetal head is used to train a probabilistic boosting tree. The fetal head image is then segmented and the BPD is computed based on the trained model.
The current approaches, however, do not consider the orientation of the BPD. This may lead to inaccurate measurements and visual quality of the BPD. For example, an error in estimating the BPD length by about 5% (˜3 mm) may result in a deviation of estimated gestational age by one week in late second trimester.
Therefore, there is a need in the art for a method and a system for providing more accurate and reliable automated techniques to estimate the gestation age of the fetus from an ultrasound image.